The present invention pertains to an apparatus for spray coating the interior surface of hollow articles and, in particular, to a spinning sprayer nozzle having a novel configuration for precisely distributing the coating material.
A typical apparatus commonly used for coating interior surfaces of hollow articles is a spin sprayer as shown in U.S. Pat. No. 3,044,441. A disadvantage of that type of spin sprayer is the difficulty encountered in producing even coatings on the interior surfaces of hollow articles which are non-circular in cross-section. That is to say that, containers with irregular cross-section such as cans for ham and other meat products which have specifically shaped cross-sections to accommodate the meat configuration are difficult to coat evenly around their inside periphery with a rotary spinning type sprayer. Candy, cocoa and institutional cans having a general square cross-sections present similar coating problems. The method of coating the interior surfaces of such containers requires a lancing movement of the sprayer such that the central axis of the spinning element is moved in and out of the container to evenly coat only the internal area as required. Such axial movements keep the distribution of coating equal from top to bottom (along the axis) of the container, and by timing the flow to continue while the sprayer is in the container, the injection of a deposit of coating material into the spinning sprayer the coating is disbursed during lancing as necessary.
To distribute the coating evenly on the interior surfaces of non-circular containers, it has been known to move the axis of the sprayer such that the inside walls are presented for coating at an equal distance around the container inside periphery. Similarly, the container can also be moving in a non-circular path perpendicular to its axis whereby the coating can be equally distributed about the interior surfaces. Either of the aforementioned techniques presents problems with regard to the mechanism designed for high-speed production of a container with an accurately and an evenly distributed coating. The previous techniques are complicated, expensive and disadvantageous for use. It is desirable that a system be used which can be readily and easily adaptable to various shape containers. Such a system would have conveying or container handling equipment similar to that required for spin spraying round (circular) containers thereby eliminating the need for the complicated movements previously set forth. To provide the equal coating distribution, a modified nozzle is disclosed for coating the inner surfaces of a container.
Another problem not easily solved by the prior art spin spraying systems, which can be handled by a modified nozzle, is the selected uneven distribution of coating. More particularly, it is sometimes desirable to apply a heavier coating to a particular inside area; for example, along the side seam of the container whereby the seam edge is given a double thickness coating. The concept disclosed herein with a relatively slight modification is easily adapted to apply a greater amount of coating in a particular preselected area.
It is an object of the invention to overcome the problems of coating containers having various cross-sectional configurations by providing an easily changed spin spray nozzle adapted to disburse a coating in accordance with the cross-section of the containers.
It is another object of the invention to provide an apparatus wherein the nozzle configuration is similar to the cross-sectional configuration of the container the nozzle is designed to coat.
It is still another object of the invention to provide a nozzle design for selected uneven distribution of coating material within a given plane such that the lancing movement of the sprayer will form a preselected distribution of coating as desired on the inside surface of a hollow container.
It is a further object of this invention to provide a low cost efficient and reliable spin sprayer which is versatile in coating containers either evenly or unevenly in accordance with the particular coating problem and requirements.
The numerous other objects and advantages of the invention will be better understood from the following description taken in connection with the drawings which disclose various embodiments each designed for a different application of the basic invention.